Method of forming brake drums



Oct. 19, 1943. c. w. SINCLAIR METHOD OF FORMING BRAKE DRUMS Filed July 14, 1941 2 Sheets-Sheet l INVENTOR.

CHARLES W. SINCLAIR BY I TTORIVEYS Oct. 19, 1943. c. w. SINCLAIR 2,332,175

METHOD OF FORMING BRAKE DRUMS Filed July 14, 1941 2 Sheets-Sheet 2 INVENTOR. CHARLES W. SINCLAIR ATTORNEYS Patented Oct. 19, 1943 METHOD OF FORMING BRAKE DRUMS Charles W. Sinclair, Detroit, Mich., assignor to Kelsey-Hayes Wheel Company, Detroit, Mich,

a corporation of Delaware Application July 14, 1941, Serial No. 402,407

1 Claim.

The invention relates to the manufacture of brake drums and refers more particularly to the method of forming brake drums from sheet metal of uniform gauge.

The invention has for one object to provide an improved method of forming a brake drum having a web of less thickness than the annular brake flange.

The invention has for another object to so form the brake drum that the steps in the method may be economically carried out.

These as well as other objects of the invention will become apparent from the following description, taken in connection with the accompanying drawings, in which Figure 1 is a side elevation of a flat circular sheet metal blank of uniform gauge from which the brake drum is to be formed;

Figures 2, 3, 4 and are sectional views illustratin successive steps in the manufacture;

Figure 6 is a sectional view illustrating the completed brake drum;

Figure '7 is an elevation thereof;

Figure 8 is a cross section on the line 88 of Figure 7.

In my method of forming brake drums, a flat circular sheet metal blank I, shown in Figure 1, is used. The blank is formed of a suitable steel and has a sufficient thickness to form the annular brake flange of the completed brake drum. The blank I is subjected to a die-pressing step to form the bowled blank 2, shown in Figur 2. The blank 2 has the Web 3 and the annular wall 4, the web being convex and extending axially beyond the annular wall. The web has the flat central portion 5 and the frusto-conical outer portion 6 which is connected to the annular wall by a gradual curve. The annular wall has the inner cylindrical portion I and the outer flared portion 8 which is gradually curved. After the bowling step has been completed the central hole 9 is formed in the central portion 5 preferably by a punch, the hole also being shown in Figure 2.

The blank is then subjected to a die-pressing step to depress the central portion of the web while maintaining the annular wall substantially unchanged, the blank ID of Figure 3 being formed. The central portion l l of the Web is hat and located axially within the unchanged annular wall of the blank and the outer portion I2 of the web is frusto-conical and connects into the cylindrical portion of the annular wall by a returnbent gradual curve. During this step, the previously formed central hole allows the metal of the web to move radially outwardly so that noticeable thinning of the web is avoided. After the depressing step the central hole I3 of larger diameter than the central hole 9 is formed in the central portion I I, preferably by a punch, the hole [3 being shown in Figure 3. The next step comprises forming and flanging the blank by necting at its inner edge into the annular flange l1 and located axially within the cylindrical portion I5, the substantially axially extending annular portion 20 connecting into the outer edge of the central portion l9, and the frustoconical outer portion 2| connecting into the annular portion 20 and the cylindrical portion I5. The hole I8 is of larger diameter than the hole I3 and the outer portion 2| is convex.

The next step comprises reducing the thickness of the web by machining the same to produce the blank 22, illustrated in Figure 5, the cylindrical portion and annular flange of the annular wall remaining unchanged. During the machining, metal is removed from the outside faces of the flat central portion and the frusto-conical outer portion and also from inside the axial flange and the substantially axially extending annular portion connecting the central and outer portions. The metal at the inner end of the cylindrical portion of the annular wall is preferably retained to reinforce the junction between the cylindrical portion and the frusto-conical outer portion of the web.

The next die-pressing step comprises ribbing and restriking the blank 22 to produce the blank 23, illustrated in Figures 6, 7 and 8. During this die-pressing step the cylindrical portion I5 of the annular wall and the radially extending annular reinforcing flange It at the outer or free end of the cylindrical portion are maintained substantially unchanged. However, the portions of the web, with the exception of the central axially extending flange 24, are radially ribbed at 25, the ribs being formed by depressing the metal toward the outer or free end of the cylindrical portion I5.

What I claim as my invention is:

The method of forming a brake drum comprising the successive steps of die-pressing a flat circular sheet metal blank of uniform gauge to shape the same into a bowled blank having an annular wall and a Web, punching the web of the bowled blank to form a central hole therethrough, die-pressing the punched bowled blank to depress the central portion of the web axially within the annular wall while maintaining the annular wall 10 substantially unchanged, die-pressing the resulting blank to shape a portion of the annular wall into a cylindrical portion and to shape the central depressed portion of the web into a generally axially extending annular flang and a generally radially extending flat portion connecting into the annular flange, then machining the web to reduce the thickness thereof, and "finally die- CHARLES W. SINCLAIR. 

